Aside from typical bacterial pneumonia, Mycoplasma pneumoniae is responsible for 30 to 40% of non-bacterial pneumonia that involves infiltrative shadows in chest radiography of lungs. Mycoplasma pneumoniae has been shown to be pathogenic among the species of Mycoplasma isolated from humans.
Mycoplasma pneumonia is common among infants and schoolchildren. The incubation period is 14 days, on average. The disease is reported to involve a wide range of complications, and in the case of children, complications such as encephalitis, Guillain-Barre syndrome and dermatitis (e.g., rashes) are developed in many cases. Though the rate of bacterial pneumonia has dramatically decreased over the last years, the percentage of mycoplasma pneumonia in all pneumonia cases has been increasing. Mycoplasma pneumoniae is the most common cause of community-acquired pneumonia after pneumococcus.
Mycoplasma is the smallest self-replicating microorganism, and cannot be easily observed with a light microscope. Unlike other bacteria, Mycoplasma lacks the cell wall, and does not respond to penicillin and the cephem antibiotics. The tetracycline antibiotics or macrolide antibiotics are commonly used for treatment.
Various methods described below are available for the diagnosis of Mycoplasma pneumoniae infections. The isolation culture method that uses a pharyngeal swab or sputum is used for a definitive diagnosis. However, the method requires a special medium and long days (2 to 4 weeks), and cannot be used for quick diagnosis. Another method detects antibodies produced in Mycoplasma pneumoniae infections. For example, serum antibodies are detected using methods such as particle agglutination (PA), and hemaggulutination reaction (IHA). However, neither of these techniques is applicable to diagnosis in the acute phase.
Determination by polymerase chain reaction (PCR) in a detection method based on the nucleic acid amplification of Mycoplasma pneumoniae in samples such as a pharyngeal swab and sputum has a strong correlation with results of the isolation culture method used to provide a definitive diagnosis. Use of LAMP (Loop-Mediated Isothermal Amplification) has also been reported as a tool simpler than PCR. However, these methods are not applicable to quick diagnosis because both PCR and LAMP involve complicated procedures, and require considerable labor for measurements.
Mycoplasma pneumonia effectively responds to only limited antibiotics, and there is a strong need at the clinic to determine the presence or absence of Mycoplasma pneumoniae infections at early stages of infection. As a rule, enzyme immunoassays (EIA) such as ELISA are applicable when specific antibodies are available. Antibodies are also applicable to various other assays such as chemiluminescence, and the dye and the fluorescence methods. However, all of these methods require dedicated measurement devices, and cannot be said as meeting the clinical needs. Immunochromatography is easy to operate, and enables a measurement in a short time period (for example, 10 to 20 min), without requiring special devices. However, it is not necessarily the case that the antibodies that are detectable by EIA are applicable to immunochromatography, and immunochromatography often requires more specific and sensitive antibodies. At present, anti-P1 protein monoclonal antibodies (PTL 1), and an immunochromatography reagent using anti-ribosomal protein L7/L12 protein-specific antibodies (PTL 2) are commercially available, and used for diagnosis of Mycoplasma pneumoniae infections. However, it cannot be said that these have high sensitivity, and that the performance is sufficient to meet the clinical needs.